1. Field of the Invention
The invention relates generally to PIN photodiodes. More particularly, the invention relates to a PIN photodiode semiconductor structure diodes used in high temperature, high humidity environments, and processes for fabrication of such devices.
2. Description of the Related Art
Fiber optic communications typically employ a modulated light source, such as a laser, a photodiode light detector, and an optical fiber interconnecting the laser and the photodiode. The laser is modulated to emit light pulses that are transmitted over an optical fiber and received at a remote unit that includes a photodiode to convert the optical signal into an electrical signal. In particular PIN diodes are widely used as the photodiodes in the optical receiver for high speed fiber optics communication. Traditionally package for these devices involve in hermetic seal in order for them to survive the high temperature, high humidity environment (HTHH). The requirement of hermetic sealing leads to complication of the device design and often results in a relatively high cost of the final product. The requirement hermetic sealing sometime can also limit the operational performance of the device, and not permit it to operate at its optimal speed.
It is highly desirable to assemble the optical receiver without hermetic sealing, which in turn requires the discrete PIN device o be able to survive under harsh operating conditions such as a temperature of 85 degrees Centigrade and 85% humidity level for more than 1000 hours. The use of a dielectric layer deposited on the top of the active region of the device substantially reduces the surface recombination related operating dark, and can increase the device lifetime as well. However, the separation or delamination of the dielectric layer away from the active region dielectric often occurs under HTHH with reverse biased operating conditions. In case the delamination bridges both anode and cathode, the dielectric passivation is broken, leading to the failure of the device.
Prior to the present invention, there has not been suitable means for prevention of delamination of the dielectric sealing layer in a PIN photodiode.